Refining hydrocarbon oils with sulfur dioxide



Ju ly l0, 1956 J. w. wl-:TZEL

REFINING HYDROCARBON OILS WITH SULFUR DIOXIDE Filed Oct. 4, 1950 E M 4m ma S E L@ w 2 m y. uw I m m m v .IIIIP-lq Iv lv M t 4, f f l z/ W w R F f F M im I .I' P M o a. `D Mm M 511D ra s @e x @m f J f .am d lv All REFININ G HYDRGCARBON OILS WITH SULFUR DIGXIDE .lohn W. Wetzel, Chester,

Corporation, ware Application October 4, 1950, Serial No. 188,283 7 Claims. (Cl. 196-14.11)

Pa., assignor to Houdt-y Process Wilmington, Del., a corporation of Delacrudes or fractions thereof certain deleterious non-hydro- 1 carbon components and contaminants, such as basic nitrogen compounds including such. nitrogen compounds which may become converted to deleterious nitrogen bases during further processing or use at elevated temperatures.

lhese nitrogen compounds when present even in relatively small amounts as of order of 1% or less in hydrocarbon charge stocks subjected to catalytic cracking, act either as transitory poisons or deactivants for the catalyst and/ or demonstrate an inhibitory eiect on the cracking reactions, resulting in reduced yields of desired conversion products, such as gasoline. The presence of these nitrogenous compounds in oil fractions or distillates which are not employed as cracking stocks also may be detrimental for certain uses; for instance in oils to be used as lubricants, fuel oils, medicinal oils, transformer oils, etc.

Liquid sulfur dioxide has heretofore been employed at low temperatures, and in substantially anhydrous state in the separation of various hydrocarbon constituents from oils, such as oletinic and aromatic hydrocarbon compounds.

It has now been found that mixtures of sulfur dioxide and Water in selected concentration and amount can be employed at ordinary or elevated temperatures for the selective extraction of basic materials from petroleum oils and other liquid hydrocarbon fractions. The presence of water in suitable amount reducesA the solubility of aromatic hydrocarbons in the sulfur dioxide under the operating conditions employed so that this material remains substantially entirely in the rainate.

In accordance with the present invention petroleum oils or other normally liquid hydrocarbon fractions containing basic compounds are treated in liquidy state with particular quantities of sulfur dioxide and Water, hereinafter specified, at ordinary or elevated temperatures, effecting selective formation of sulte addition compounds of the bases which are collected in an aqueous acid layer readily separated from the oil raffinate. The acid layer containing the addition salts of the bases is regenerate the sulfur dioxide for further use in the process While setting free the bases in a condition such that they are readily separated from the aqueous acid extract.

There is thus obtained by the process of the invention a hydrocarbon fraction of reduced nitrogenous content which may provide an improved material for charging to a catalytic cracking or other catalytic hydrocarbon decomposed to conversion operation. From the acid extract available nitrogenous fractions or compounds can be economically recovered by suitable methods of fractionation or by hydrogenolysis, with or without previous separation into fractions, as more particularly described in my copending application Serial No. 128,761 of November 22, 1949 now Patent No. 2,704,758.

In a typical operation in accordance with the invention the oil to be extracted is contacted with a mixture of SO2 and water containing an amount of SO2 in excess of the stoichiometric quantity required to form sulfurous acid, at a temperature sumciently high to reduce the viscosity of the oil, if necessary, and under atmospheric or superatmospheric conditions required to retain the oil in liquid state. The oil and sulfur dioxide-water extractant are thoroughly agitated as by stirringV if batch operation is employed, or by countercurrent ow of oil and aqueous acid mixture in a suitable tower, one form of which is hereinafter described, There is thus obtained on subsequent settling, an acid layer containing base sultes soluble therein and an oil layer readily separable therefrom. By distillation of the acid layer SO2 is volatilized leaving a still residue of bases and water which are separated by settling. lf low molecular weight bases are present to any significant extent, these may be separated from the Water layer by salting out.

The proper selection of the proportions of sulfur dioxide to oil and the concentration of sulfur dioxide with respect to the water are of the utmost importance. lt has been found that for the desired extraction of nitrogenous bases from oils containing the same Without accompanying removal of large quantities of hydrocarbon components of the oil, the sulfur dioxide can be effectively employed in weight ratios of from about l5 to 150% by weight of the oil, and preferably at 30 to 50% by Weight of the oil. The quantity of water used should be in excess of that which will dissolve in the oil. With most oils of the type described and under the extraction conditions employed, a quantity of water equal to at least about 0.5% and up to about 5.0% by weight of the oil is to be used. The quantity of Water, also, should be less than the stoichiometric quantity required to form sulfurous acid with the SO2 employed, so that SO; is always present in excess. Use of larger quantities of water, as above 5.0% by weight of the oil, necessitates an increased sulfur dioxide content in the extractant to obtain the same extent of extraction ofY nitrogenous bases.

With increasing ratios of SO2 to oil more aromatics are dissolved in the extract with the tendency toward the formation of tarry materials interfering with extraction. If insuiicient SO2 is employed, nitrogen bases are not extracted or are extracted to only a minor extent comprising chiefly the strong nitrogen bases which form stable acid sulfites that are not readily hydrolyzable. On the other hand by using the proportions of S02 and water within the range set out above, hydrolysis of even the weakest nitrogen base acid suliite salts is prevented and these weak bases are removed in the extract along with the strongly basic compounds.

Fairly light hydrocarbon oils, such as those having a gravity and viscosity in the range of gasoline and' kerosene, may be extracted at room temperatureV and under atmospheric pressure. With heavier or more viscous oils temperatures should be raised suf'ciently to reduce the viscosity of the oil to facilitate admixture with the extractant, the pressure being raised suliicientlyto maintain the oil in liquid state. Thus for instance with a light gas oil of about 20 to 25 API gravity, temperatures of 1Z0-150 F, may be employed andl pressures from about 50-300 pounds per square inch gauge.

In the accompanying drawings there is shown a ow diagram illustrating a preferred methodt ofA carrying'out the extraction in a continuous countercurrent extractor. If desired the extractor may be packed to provide better contacting of the extractants with the oil. It will be understood that in practical operation the inlet lines for SO2 and sulfurous acid should be provided with diiusers, spray nozzles, etc. to obtain intimate mixing.

After equilibrium is established in the system there will be contained in the tower 1 stratied layers of oil, sulfurous acid and base sullites. In the operation of the system, the charge stock to be extracted is introduced into the extractor below the interface of the oil-sulfurous acid for initial admixture with the sulfurous acid, the raihnate being removed near the top of the oil layer as indicated at B. Moist sulfur dioxide is introduced directly into the oil as indicated at C and passes upwardly through the oil, unreacted SO2 being removed above the oil layer at D and recirculated. The SO2 passing throughV the oil effects desired agitation of the oil. The moisture content of the SO2 stream is maintained by introducing steam into the line entering at C. Sulfurous acid and base sultites separate out from the oil layer and form on settling separate layers with the base sultes below the sulfurous acid. A portion of the sulfurous acid is continuously withdrawn from that layer, as indicated at E, and returned to the top of the oil layer at F to cascade countercurrently through the oil. Water may be added in the sulfurous acid line to maintain the required water content of the system, or alternatively all of the makeup water may be supplied by the steam admitted to the SO2 stream.

The raffinate removed at B is relatively free from basic constituents and contains dissolved and entrained sulfur dioxide and sulfurous acid. This raffinate is passed into a degasser 2, maintained at lower pressure than the extractor and at a temperature below the initial boiling point of the oil. From the degasser extracted oil is removed, which is suiciently free from sulfur dioxide for most practical purposes. Last traces of sulfur dioxide may be removed from the oil by washing with dilute caustic. The SO2 from the degasser, which may contain a small amount of water is sent to storage vessel 3, to be recycled in the process with the addition of makeup SO2 as required.

The basic sullites are removed from the bottom of the extractor G and subjected to ash distillation 4 at temperatures effecting thermal decomposition of the sultes, obtaining an overhead stream of SO2 and the free nitrogen bases as a residue. The sulfur dioxide overhead from flash distillation is sent to storage vessel 3 and is recycled.

Instead of thermally decomposing the nitrogen base suliites, the Vfree bases may be released by hydrolysis with or without the presence of a small amount of caustic.

In a properly balanced system the amount of water added as steam to the SO2 line or for dilution of the sulfurous acid from E in that line, or both, will be sucient to keep the level of the H2803 layer below the oil fairly constant.

The method above described is particularly attractive because of the facility of separating the oil and the base sultes, and is economically desirable from the standpoint of low cost operation as a result of good recovery of SO2 for recycling.

By the methods of the invention not only can there be refined and improved oils required for use as charging stock to catalytic cracking or other catalytic conversion, but also other hydrocarbon fractions such as gasolines, fuel oils, light naphthas, kerosene, or diesel fuels, may be treated to improve color and oxidation stability and render them more resistant to sludge formation and other undesirable side reactions. In addition, heavier oils such as lube oils, transformer oils, etc. can be beneficially improved by the described treatment.

Example A Los Angeles Basin gas oil boiling in the range 7 440950 F. and containing 0.39% by weight N and 1.08% S, was subjected to flash vaporization and the overhead subjected to extraction with SO2 and water under the conditions indicated in the Vfollowing table and with the results therein tabulated:

Vt. Oil, g.. 1,116.2 1, 211 1,142 W't. H2O, g. 25 50 50 Wt. SO2, g 510. 8 1, 225 1, 840 Wt. percent H2O in Liquid Charge 1.8 2. 2 4. 0 4. 2 Wt. percent SO: Based on Oil-i- 2 16 45 97 154 Maximum Pressure, p. s. i. g.. 300 300 Temperature, F., approx 80 125 180 180 Product:

Wt. percent N in Raftinate 0.26 0.26 0. 23 0.20 Wt. percent S in Ranate 1. 05 0. 95 Percent N Removed 30 30 41 48 Vol. percent Extract ca. 4

For oils of lower specific gravity than water and having a low viscosity, as up to about that of kerosene, extraction is readily carried out at room temperature; higher temperatures may be employed, if desired, even for such oils. For more viscous oils and particularly those having a high specific gravity, heating is essential to facilitate good contact between the oil and the sulfur dioxide. Whenever elevated temperatures are employed, the pressure should also be raised to an extent at least sucient to maintain the oil in liquid state. In the cold, as at temperatures of about and below 0 C., selective extraction of nitrogen bases is not obtained, since the dissolution of aromatics or other hydrocarbons is favored thereby.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim as my invention:

1. The method of rening hydrocarbon oils boiling above the range of gasoline which comprises extracting such oils in liquid state and at normal to elevated temperatures with a mixture of sulfur dioxide and water, separating the thus formed aqueous acid layer from the oil rafnite, decomposing sultite addition compounds present in the aqueous acid extract to regenerate sulfur dioxide, and then separating from the extract organicbases set free by such decomposition, the mixture of water and sulfur dioxide employed in said extracting containing water in excess of its solubility in the oil and from 0.5 to 5% by weight of the oil and containing SO2 in excess of the stoichiometric quantity required to form sulfurous acid with the water present, said mixture being vemployed in quantities providing 15 to 150% SO2 by weight of the oil.

2. The method according to claim l wherein said mixture is employed in proportions furnishing 30 to 50% SO2 by weight of the oil.

3. 'Ihe method of preparing a charge stock for catalytic cracking which comprises removing contaminating nitrogenous bases from'a hydrocarbon oil boiling in a range above gasoline, byextraction with a mixture of sulfur dioxide and water at elevated temperature and at a pressure suicient to maintain the oil in liquid state, the mixture of sulfur dioxide and water containing SO2 in free and combined state-equal to 15 to 150% by weight of the oil and water in excess of its solubility in the oil but not more than 5% by weight of the oil, and separating the thus formed aqueous acid layer from the oil raffinate.

4. The method according to claim 3 wherein said mixture is employed in proportions furnishing 30 to 50% SO2 by weight of the oil.

5. The method of extracting nitrogenous bases from hydrocarbon oils boiling above the range of gasoline, which comprises passing moist SO2 upwardly through a body of such an oil whilesurnultaneously passing sulfurous acid downwardly through said oil, said sulfurous acid forming a layer below said body of oil, and an aqueous layer containing addition compounds of such nitrogenous bases in the form of sultites being formed below said sulfurous acid layer, continuously admitting oil to be treated at the bottom of said body of oil and removing oil rainate near the top thereof, removing SO2 in vapor phase above said body of oil, adding moisture to said SO2 and recirculating for further upward passage through said body of oil, withdrawing sulfurous acid from said layer thereof and recirculating the same to the top of said body of oil, continuously withdrawing the aqueous layer containing said addition compounds, decomposing said addition compounds to free the nitrogenous bases, separating the freed bases from the aqueous residue, said SO2 and oil being continuously supplied in the proportions of 15-150% SO2 by weight of the oil, and said water being maintained at 0.5 to 5% by weight of the oil.

6. The method according to claim 5 wherein the oil and SO2 are continuously supplied for said extracting in the proportions of 30 to 50% SO2 by Weight of the oil.

7. In the extraction of heated hydrocarbons with a solvent consisting predominantly of liquid SO2, the method of repressing the extraction of aromatic and olenic constituents and enhancing the extraction of nitrogenous materials from the hydrocarbon layer into the SO2 layer which consists of maintaining in the SO2 a signicant amount of water, less than the stoichiometric quantity required to form sulfurous acid, and less than 5% by weight of the hydrocarbon, but more than 0.5% of the hydrocarbon, said mixture of SO2 and water being employed in portions furnishing 15-150% SO2 by weight of the hydrocarbon.

References Cited in the le of this patent UNITED STATES PATENTS 146,405 Schalk Ian. 13, 1874 215,756 Kirk May 27, 1879 1,042,915 Hirschberg Oct. 29, 1912 1,855,486 Morrell et al Apr. 26, 1932 1,965,828 Fox July 10, 1934 2,035,583 Bailey Mar. 31, 1936 2,189,278 Bailey et al. Feb. 6, 1940 FOREIGN PATENTS 3,759 Great Britain 1876 186,738 Great Britain Oct. 12, 1922 

1. THE METHOD OF REFINING HYDROCARBON OILS BOILING ABOVE THE RANGE OF GASOLINE WHICH COMPRISES EXTRACTING SUCH OILS IN LIQUID STATE AND AT NORMAL TO ELEVATED TEMPERATURES WITH A MIXTURE OF SULFUR DIOXIDE AND WATER, SEPARATING THE THIS FORMED AQUEOUS ACID LAYER FROM THE OIL RAFFINITE, DECOMPOSING SULFITE ADDITION COMPOUNDS PRESENT IN THE AQUEOUS ACID EXTRACT TO REGENERATE SULFUR DIOXIDE, AND THEN SEPARATING FROM THE EXTRACT ORGANIC BASES SET FREE BY SUCH DECOMPOSITION, THE MIXTURE OF WATER AND SULFUR DIOXIDE EMPLOYED IN SAID EXTRACTING CONTAINING WATER IN EXCESS OF ITS SOLUBILITY IN THE OIL AND FROM 0.5 TO 5% BY WEIGHT OF THE OIL AND CONTAINING SO2 IN EXCESS OF THE STOICHIOMETRIC QUANTITY REQUIRED TO FORM SULFUROUS ACID WITH THE WATER PRESENT, SAID MIXTURE BEING EMPLOYED IN QUANTITIES PROVIDING 15 TO 150% SO2 BY WEIGHT OF THE OIL. 